Use bash features to improve $distfiles parsing.

That means that it's not necessary anymore to use an '@' before the
extract suffix string. yay.

--HG--
extra : convert_revision : 83ce2c783cb917ef59b87eacb0565cfcff277218

templates/sudo.tmpl

@@ -2,7 +2,7 @@
 pkgname=sudo
 version=1.6.9p17
 patch_files="$pkgname-Makefile-in.diff"
-distfiles="http://www.courtesan.com/sudo/dist/$pkgname-$version@.tar.gz"
+distfiles="http://www.courtesan.com/sudo/dist/$pkgname-$version.tar.gz"
 build_style=gnu_configure
 configure_args="--disable-root-mailer"
 short_desc="Allow others to run commands as root"